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416 P A R T III / Assessment of Heart Disease
DISPLAY 18-4 Atrial Fibrillation Ablation: Definitions, Indications, Technique, and Laboratory Management
AF definition:
• Paroxysmal AF is defined as recurrent AF ( 2 episodes) that terminates spontaneously within 7 days.
• Persistent AF is defined as AF, which is sustained beyond 7 days, or lasting less than 7 days but necessitating
pharmacologic or electrical cardioversion.
• Longstanding persistent AF is defined as continuous AF of greater than 1-year duration.
• The term permanent AF is not appropriate in the context of patients undergoing catheter ablation of AF as it refers to a
group of patients where a decision has been made not to pursue restoration of sinus rhythm by any means, including
catheter or surgical ablation.
Indications for catheter AF ablation:
•Symptomatic AF refractory or intolerant to at least one Class 1 or 3 antiarrhythmic medication.
• In rare clinical situations, it may be appropriate to perform AF ablation as a first-line therapy.
• Selected symptomatic patients with heart failure and/or reduced ejection fraction.
• The presence of an LA thrombus is a contraindication to catheter ablation of AF.
Indications for surgical AF ablation:
•Symptomatic AF patients undergoing other cardiac surgery.
• Selected asymptomatic AF patients undergoing cardiac surgery in whom the ablation can be performed with minimal
risk.
• Stand-alone AF surgery should be considered for symptomatic AF patients who prefer a surgical approach, have failed one
or more attempts at catheter ablation or are not candidates for catheter ablation.
Preprocedure management
• Patients with persistent AF who are in AF at the time of ablation should have a TEE performed to screen for thrombus.
Technique and laboratory management:
• Ablation strategies which target the PVs and/or PV antrum are the cornerstone for most AF ablation procedures.
•If the PVs are targeted, complete electrical isolation should be the goal.
• For surgical PV isolation, entrance and/or exit block should be demonstrated.
• Careful identification of the PV ostia is mandatory to avoid ablation within the PVs.
• If a focal trigger is identified outside a PV at the time of an AF ablation procedure, it should be targeted if possible.
• If additional linear lesions are applied, mapping or pacing maneuvers should demonstrate line completeness.
• Ablation of the cavotricuspid isthmus is recommended only in patients with a history of typical atrial flutter or inducible
cavotricuspid isthmus dependent atrial flutter.
• If patients with longstanding persistent AF are approached, ostial PV isolation alone may not be sufficient.
• Heparin should be administered during AF ablation procedures to achieve and maintain an ACT of 300 to 400 seconds.
Adapted from Calkins, H., Brugada, J., Packer, F., et al. (2007). HRS/EHRA/ECAS expert consensus statement on catheter and surgical ablation of atrial fibrillation:
Recommendations for personnel, policy, procedures and follow-up. Heart Rhythm, 4(6), 816–861.
origin of the tachycardia. The earliest endocardial atrial electro- VT associated with coronary heart disease is usually caused
gram marks the origin of the tachycardia. 75 by a reentrant mechanism in an area of patchy fibrosis or scar.
One of the problems encountered with ablating in this situation
Ventricular Tachycardia is that these patients may have multiple tachycardia circuits. 59
Ablation of paroxysmal VT can be a challenging therapy for pa- 3-D electroanatomic voltage maps can be used to reconstruct
tients whose tachycardia is suited to study and ablation. For a VT the region of scar within the ventricle and identify the critical
focus to be ablated, the tachycardia must be inducible, monomor- zones of conduction delay responsible for reentrant VT. This
phic, and tolerated for long enough periods to enable accurate technique is known as “substrate mapping.” Ablation is em-
mapping. The advent of electroanatomic and noncontact 3-D map- ployed to eliminate potential reentrant circuits and can be per-
ping systems has greatly facilitated mapping and ablation of VT. 76 formed during sinus rhythm. Induction and mapping of the VT
For a successful ablation, the type of VT must be determined. is not required prior to ablation. If a single monomorphic VT is
Bundle-branch reentrant tachycardia conducts antegrade identified, the earliest site of activation during VT also can be
over the right bundle and retrograde over the left bundle. This located and ablated using these mapping systems. 76 Techniques
type of VT occurs in patients who have severe ischemic or idio- to identify the best ablation strategy for VT are still under de-
pathic cardiomyopathy. The VT is rapid because it uses the velopment.
His–Purkinje system. Ablation of the right bundle usually abol-
ishes this VT. 77
Benign monomorphic VT (idiopathic VT) typically occurs in
young people with no structural heart disease. The VT most often NURSING CARE OF THE PATIENT
arises from the right ventricular outflow tract or from the inferior UNDERGOING EP PROCEDURES
left ventricular septum (fascicular VT). Various EP techniques are
used to map the presumed site of origin before ablating. RF abla- Health care professionals caring for arrhythmia patients play a
tion is most often successful in this group of patients. pivotal role for the patient undergoing an EP procedure,